1. Field of the Disclosure
The present disclosure relates to communications systems and more specifically to synthetic loss measurements using session numbers.
2. Description of the Related Art
A communication network may include network elements that route packets through the network. Some network elements may include a distributed architecture, wherein packet processing may be distributed among several subsystems of the network element (e.g., line cards).
Service Operation, Administration, and Management (“Service OAM” or “SOAM”), is defined by ITU-T Y.1731/IEEE 802.1ag and defines Maintenance Entity Group End Points (MEPs) and Maintenance Entity Group Intermediate Points (MIPs) that may be provisioned on a network element. Throughout this disclosure, MEPs and MIPs may generally be referred to as “maintenance points.” A maintenance point may be associated with a particular maintenance level (e.g., 0 to 7) and may be configured to communicate traffic to a peer maintenance point at the same maintenance level that resides in the communication network. The maintenance entities of a maintenance entity group are maintenance points comprising end points (e.g., MEPs) and intermediate points (e.g., MIPs). The maintenance points may represent entities that are provisioned within a network element. An end point is a maintenance functional entity implemented at the ends of a maintenance entity group. An end point may generate and receive packets such as OAM frames. An intermediate point represents a maintenance functional entity between end points. An intermediate point responds to packets received from end points and may forward these packets to downstream intermediate points and end points.
From time to time, maintenance points may perform data loss measurements to characterize network performance between two or more MEPs. The data loss measurements may be employed using payload data or using synthetic data, the latter of which is also referred to as synthetic loss measurement (SLM) as specified by ITU Y.1731. During synthetic loss measurement, synthetic data frames are transmitted between at least two MEPs and are counted by at least one receiving MEP. By counting the actual number of transmitted and received synthetic data frames during a measurement period, a frame loss ratio and/or other frame loss parameter may be determined and may be used to characterize performance of the measured network segment.
In various embodiments, network elements may also employ link aggregation. Link aggregation (e.g., as specified by IEEE 802.1AX-2008) may generally describe the practice of using multiple network cables or ports in parallel to increase the link speed beyond the limits of any one single cable or port, and to increase redundancy for higher availability. In link aggregation, a group or set of ports may be combined and represented as a single logical port to other components of the network system. Various switching elements of the network system may “see” the aggregated ports (known as a “link aggregation group” or “LAG”) as a single logical communication port in the routing tables or databases of network elements external to the LAG.
In equipment that is undergoing a conventional synthetic loss measurement, a lack of statefulness among MEPs may result in measurement errors. This kind of measurement error may occur in various kinds of network equipment and particularly when the transmitting and receiving MEPs do not otherwise share state information with each other.